This invention relates generally to control apparatus for transit vehicles and, in particular, to series parallel control and power brake control apparatus. Series parallel control and power brake control for operating the traction motors of a typical transit vehicle are known int he art such as disclosed in the Westinghouse Engineer, March, 1973, Volume 33, Number 2 in an article entitled "Alternative Systems for Rapid-Transit Proplusion and Electrical Braking" by B. J. Krings, which article is incorporated herein by reference. The article discusses the use of a series parallel controller and a power-brake controller in a motor circuit. As discussed in the article with regard to cam-controlled equipment, in the motoring mode the four motors of the transit vehicle are initially connected in series with the acceleration resistors (Figure 1a of the article). To accelerate, the propulsion cam controller progressively reduces the amount of resistance in series with the motors. When all of the accelerating resistors are shorted out, cam switches in a two-position controller called the series-parallel controller (SPC) make a transistion in motor connections: they reconnect the motors with two in series and the two groups of two motors in parallel. For dynamic braking, the motors are first disconnected from the DC power source, then the cam switches of the two-position controller called the power-brake changeover (PBC) reconnect the motors as parallel generators across the braking resistor as discussed previously (FIG. 2 of the article).
U.S. Pat. No. 3,218,537 issued to John J. Stamm dated Nov. 16, 1965 and assigned to the present assignee also discloses motor acceleration and braking control for a transit system.
In U.S. Pat No. 4,458,185 dated July 3, 1984 issued to Thomas C. Matty et al. and assigned to the present assignee, which is incorporated herein by reference, is disclosed a cam controller apparatus for an electric motor including a cam controller coupled with a current control means that is movable through successive angular positions for sequentially removing one or more selected resistors from the electric motor citcuit. The control apparatus also includes stepping motor means coupled with a cam controller for providing a predetermined angular position movement of the cam controller.
Although the prior art has taught the use of single cam shafts for the accelerating resistors and braking resistors in the cam-controlled motor circuit for a transit vehicle as disclosed in the Matty patent, the prior art teaches separate control apparatus for the series to parallel changeover controller and power-brake controllers. This may lead to difficulty with synchronization of the two controllers.